Method of making a subsurface well safety valve

ABSTRACT

A subsurface safety valve is made by the steps of coating a hard seat in the inside surface of a circular tubular member, honing the inside of the tubular member, drilling a hole in a circular plane perpendicular to the axis of the tubular member to form hinge holes in the future cut out valve closure members, and then cutting hinges out of circular sectors of the tubular member. Preferably the cutting is performed using a wire electrode of a wire cutting electric discharge machine, although cutting may be performed by a mill or a chemical machine.

This is a division of application Ser. No. 07/404,241, filed 09/07/89now U.S. Pat. No. 4,926,945.

BACKGROUND OF THE INVENTION

It is known that a curved or arcuate flapper valve may be used in asubsurface well safety valve to provide a larger bore in the safetyvalve as compared to a flat flapper valve. Such valves as described inU.S. Pat. Nos. 2,162,578; 4,531,587; and U.S. patent application Ser.No. 07/255,818, filed Oct. 11, 1988, are designed to provide largerbores and thus increase the well production through the valve. However,such valves were complicated to manufacture generally requiring amulti-axis mill and were quite expensive. Conventional curved flappersutilize a seat which required developing the seat line by two diameters.Furthermore, the prior art curved flapper valves, which were operated bya flow tube, retracted the flow tube away from the flapper in the closedposition thereby increasing the length, expense and spring-operatingparameter requirements.

The present invention is directed to an improved well safety valvehaving a curved flapper in which the flapper has a sealing surface onits interior or inside diameter and developed by one diameter asdistinguished from valves having a seat surface developed by twodiameters. Furthermore, the present valve includes a flow tube having alower end contoured to coact with the flapper for reducing the overalllength of the safety valve, reducing the required spring parameters, andthereby reducing the cost of the valve. Furthermore, the method ofmaking the flapper of the present invention provides flappers bydifferent manufacturing methods whereby the cost of the flapper issignificantly reduced from curved flappers manufactured on multi-axismilling machines.

SUMMARY

One feature of the present invention is the provision of a subsurfacewell safety valve for controlling the fluid flow through a well conduitwhich includes a housing having an axial bore therethrough and a valveseat positioned in the housing. A valve closure member is movablebetween open and close positions relative to the valve seat and thevalve closure member is a sector of a cylinder having a concave surfacewhich forms a sealing surface. The valve seat has a seating surfacecontoured to coact with the sealing surface. A flow tube istelescopically movable in the housing for controlling the movement ofthe valve closure member and the lower end of the flow tube has asurface having a contour substantially equal to the contour of theconcave seating surface. Preferably, the contour of the lower end of theflow tube is a cylindrical surface having a radius substantially equalto the radius of the concave sealing surface. Hydraulic piston andcylinder means are provided in the housing for actuating the flow tube.

Still a further object of the present invention is wherein the lower endof the flow tube is positioned closely adjacent the concave sealingsurface of the valve closure member when the safety valve is in theclosed position. This reduces the travel required of the flow tube,reduces the length of the safety valve, reduces the requirements of thespring biasing means, reduces the spring requirements, and consequently,reduces the valve cost.

Yet a still further object of the present invention is the provision ofa resilient seat encircling the valve seat and having a seating surfacecontoured to coact with the sealing surface.

Yet a further object of the present invention is the method of making anarcuate valve closure member for a subsurface well safety valve whichincludes honing the inside of a circular tubular member for providing afinished concave sealing surface and cutting a circular sector with ahinge out of the tubular member.

Still a further object of the present invention is cutting a secondcircular section with a hinge out of the tubular member wherein thesecond sector is diametrically opposite to the first sector. Preferably,the method includes wherein the first and second sectors and hinges aresimultaneously cut out of the tubular member.

Yet a further object is wherein the cutting is performed by anelectronic discharge machine.

A still further object is wherein holes are drilled into the tubularmember before cutting out the circular sectors and hinge for forming ahinge hole in the cutout valve closure member. Preferably, the hingeincludes a longitudinal axis and the hinge axis is cut out of a portionof the tubular member which is parallel to the longitudinal axis of thetubular member.

Yet a still further object of the present invention is applying asprayed on hard seat to the inside of the tubular member prior tohoning.

A still further object is the provision of a molded ceramic seat forproviding a high compressive strength material which is corrosionresistant.

Other and further objects, features and advantages will be apparent fromthe following description of a presently preferred embodiment of theinvention, given for the purpose of disclosure and taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B and 1C are continuations of each other an re an elevationalview, partly in cross section, illustrating a valve using the presentinvention and shown in the open position,

FIG. 2 is an exploded perspective view of the curved flapper of thepresent invention and its coacting parts,

FIG. 3 is an elevational view illustrating the method of making a curvedflapper according to the present invention,

FIG. 4 is a cross-sectional view taken along the line 4--4 of FIG. 3,

FIG. 5 is an elevational perspective of FIG. 4,

FIG. 6 is a fragmentary elevational view, partly in cross section, ofthe valve shown in the closed position.

DESCRIPTION OF THE PREFERRED EMBODIMENT

While the present invention may be utilized in various types andconfigurations of subsurface well safety valves, it will be described,for purposes of illustration only, of the type shown in patentapplication Serial No. 07/255,818, as this embodiment provides a safetyvalve with a maximum bore opening.

Referring now to the drawings, and particularly to FIGS. 1A, 1B and 1C,the reference numeral 10 generally indicates a retrievable subsurfacetubing safety valve which includes the present invention. The valveincludes a housing 12 and is adapted to be set in or retrieved from awell tubing which includes a landing nipple generally indicated by thereference numeral 11 to permit well production therethrough under normaloperating conditions, but in which the safety valve 10 may be closed inresponse to abnormal conditions.

The valve 10 includes an axial bore 14, a curved valve seat 16 (FIG. 1C)positioned about the bore 14 in the housing 12, a valve closure membersuch as curved flapper 18 which is in the form of a curvedcross-sectional shape, as will be more fully discussed hereinafter, isconnected to the body 12 by pivot pin 20. Thus, when the flapper 18 isin the upper position and seated on the valve seat 16 (FIG. 6), thesafety valve 10 is closed blocking flow upwardly through the bore 14 andwell tubing. A flow tube or longitudinal tubular member 22 istelescopically movable in the body 12 and through the valve seat 16. Asbest seen in FIG. 1C when the flow tube 22 is moved to a downwardposition, the tube 22 pushes the flapper 18 away from the valve seat 16.Thus, the valve 10 is held in the open position so long as the tube 22is in the downward position. When the tube is moved upwardly, theflapper 18 is allowed to move upwardly onto the seat 16 by the action ofa spring 24 and also by the action of fluid flow moving upwardly throughthe bore 14.

The flow tube 22 is biased in an upward direction by a suitable meanswhich may include a spring 26 (FIG. 1B) for yieldably urging the flowtube 22 in an upward direction to release the flapper 18 for closing thevalve 10. The safety valve 10 is operated by the application or removalof a pressurized fluid, such as hydraulic fluid, through a control pathor line such as control line 36 extending to the well surface from aport 38 in the housing 12 for supplying pressurized fluid to the top ofa piston and cylinder means or assembly generally indicated by thereference numeral 40. The assembly 40 includes a piston 42 movable in acylinder 44, one of which, here shown as the piston 42, may be connectedto the flow tube 22 by a tongue and groove connection 46.

As best seen in FIG. 1C, a nose, generally indicated by the referencenumeral 50, is provided which is positioned in the landing nipple 11 inthe bottom of the housing 12. The nose 50 includes a body 52 and meansfor connection to the inside of the nipple 11 such as collet fingers 54which engage and latch into a nose latching recess 58 in the landingnipple 11. The body 52 carries a seal 60 for engagement by the flow tube22 when it is in the downward position. When the valve is in the openposition and the flow tube 22 seats against the seal 60, the flapper 18and valve seat 16 are protected against erosion by production fluid. Thenose 50 may be installed into the landing nipple 11 by a suitable wellprong which lowers the nose 50 into the nipple 11 until the fingers 54engage the recess 58 at which time the prong may be released from thenose 50 and retrieved. Thereafter, the housing 12 of the safety valve 10is installed in the landing nipple 11.

Referring now to FIG. 1A, the valve 10 is generally run into the wellconduit and landing nipple 11 on a wireline or pumpdown, for example, aCamco wireline running tool. The housing 12 includes suitable means forconnection to the inside of the landing nipple 11 such as locking dogs70 which are in the retracted position while being run in but are hereshown as set in a housing latching recess 72 in the landing nipple 11.The housing is normally run into the nipple 11 until a no-go shoulder 74on the housing 12 engages a stop shoulder 76 in the landing nipple 11.Thereafter, a sleeve 78 is moved downwardly to latch the dogs 70outwardly into the recess 72. The sleeve 78 is held in a releasablylatched position by collet fingers 80 and pins 82 biased inwardly by agarter spring 84.

The above description is generally disclosed in patent application Ser.No. 07/255,818, which is herewith incorporated by reference.

Referring now to FIGS. 1C, 2 and 6, the coaction between the valveclosure member or flapper 18 and its coacting elements of the valve 10is best seen. First, the flapper 18 is a sector of a cylinder andincludes an internal diameter or concave surface 19 which forms asealing surface. The valve seat 16 includes a coacting seating surfacecontoured to coact with the sealing surface 19. Preferably, the valveseat 16 is metal to form a metal-to-metal seal with the flapper 18. Inaddition, if desired, a soft seat insert 17 may be provided positionedabout the outer periphery of the hard seat 16 and which is alsocontoured to coact with the sealing surface 19. The soft seal 17 may beof any suitable material such as an elastomer. However, if desired, theseat 16 may be a molded ceramic insert which Provides a low cost hardseat. The ceramic seat has a high compressive strength and is corrosionresistant. Any suitable ceramic may be used such as silicon nitride ofzirconia. In any event it is preferable for the seat 16 to have athermal fit and/or brazed or welded to the metal housing 12.

FIG. 1C illustrates the position of the valve closure member 18 and flowtube 22 when the valve 10 is in the open position, and FIG. 6illustrates the position of these elements when the valve 10 is in theclosed position. Referring to FIGS. 1C, 2 and 6, it is to be noted thatthe lower end 23 of the flow tube 22 has a surface 23 having a contoursubstantially equal to the contour of the concave sealing surface 19 ofthe flapper 18. That is, the lower end 23 of the flow tube 22 is acylindrical surface having a radius substantially equal to the radius ofthe concave sealing surface 19. This feature advantageously allows thelower end 23 of the flow tube 22 to be positioned closely adjacent tothe concave sealing surface 19 of the valve closure member or flapper 18when the safety valve 10 is in the closed position as best seen in FIG.6. That is, if the lower end of the flow tube 22 were flat, the flowtube 22 must be retracted a greater distance in order to allow theflapper 18 to close. However, if the contour of the lower end of theflow tube 22 is the same as the internal diameter 19 of the flapper 18or less, the contact point between the flow tube 22 and the flapper 18will begin to open the flapper 18 immediately on downward movement ofthe flow tube 22. Thus, the stroke of the flow tube 22 will be the sameas in conventional flat flapper valve closure element valves. Withoutthe contour of lower end 23, the flow tube 22 would be required toretract a greater distance lengthening the length of the safety valve10, increasing its cost, requiring greater strength and expense out ofthe biasing spring 26, and undesirably increasing the spring 26 spread.

Since it is desired that the lower end 23 of the flow tube 22 cover theflapper 18 when it is in the open position, as best seen in FIG. 1C, andprotect the flapper 18 from erosion, the contour 60 of the nose seal iscontoured to mate with and coact with the lower end 23 of the flow tube22.

Previously manufactured arcuate flappers generally require multiplediameters to define the flapper sealing surface, and required multipleaxis milling machines to manufacture the flapper. However, by using asingle diameter to obtain the sealing surface 19, it has been found thatby using the present method of manufacture that flappers can bemanufactured at significantly lower costs.

The method of making the arcuate valve closure member or flapper 18 fora subsurface well safety valve is best seen in FIGS. 3, 4 and 5. First,a length of a circular tubular member 90 is provided of whatever type ofmetal it is desired to make the flappers 18. The inside 92 is honedwhereby the internal diameter of the tube 90 provides the finishedsealing surface 19 for the flappers 18. The length of the tubular member90 is selected depending upon the number of flappers 18 it is desired tomanufacture at one time. In the example given in FIGS. 3, 4 and 5, asufficient length of tube is shown to manufacture four flappers 18 forpurposes of illustration only. If desired, the internal diameter orsealing surface 92 may be provided with a hard seat such as by ceramicspray such as zirconia or silicon nitride. This provides a low cost hardsealing. Of course, with a coating, the internal diameter 92 would thenbe honed or lapped, such as to a 0.020 micron finish. In any event, itis preferable to hone or lap the interior 92 of the tubular member 90 toprovide all of the sealing surfaces for a multiplicity of flappers 18which are to be manufactured out of the tubular member 90.

Next, it is desired to drill holes 94 in the tubular member 90 beforemachining the flappers 18. The drilled holes 94 form the hinge holes 21in the hinges 25 of the flappers 18.

Thereafter, when the flappers 18 along with their hinges 25 are cut outof the tubular member 90, the hinge holes 21 are all prepared to receivethe pivot pin 20 (FIGS. 1C, 6 and 2). The hinge 25 includes alongitudinal axis and the hinge axis is preferably cut out of a portionof the tubular member 90 which is parallel to the longitudinal axis ofthe tubular member 90. That is, the holes 94 are drilled through thetubular member 90 in a circular plane that is perpendicular to the axisof the tubular member thereby forming hinge holes in the cutout valveclosure member or flapper 18.

The sealing surface 19 of the flappers 18 is formed by two right-angleintersections of a cylindrical tube, preferably, the cutting operationis performed by rotating the tubular member 90 about its own axis sothat the cutting tool 96 defines a cylindrical surface and the peripheryof the hinges 25. Preferably, the cutting tool 96 is an electricdischarge machine although a regular mill or chemical machines, may beutilized. In any event, the cutting tool 96 cuts a circular section outof the tubular member 90 with a hinge. Preferably, a second circularsector with a hinge is also cut out of the tubular member wherein thesecond sector is diametrically opposed to the first sector. Thus, asbest seen in FIG. 3, first and second flapper valves 18a and 18a are cutout of the tubular member 90 and the flappers 18a and 18b arediametrically opposite to each other in the tubular member 90.Preferably, the cutting tool 96 simultaneously cuts out both flappers18a and 18b at the same time.

In addition, referring to FIG. 2, the coacting surfaces on the flow tube22 and the nose seal 60 may be cut out of a single tubular member forreducing cost and insuring a mating fit between the members 22 and 60.Similarly, the hard metal seat 16 and the soft metal seat 17 may besimultaneously made by telescoping a tubular soft material over atubular hard material and simultaneously cutting the surfaces 16 and 17.Therefore, the present manufacturing method provides a quick,inexpensive, but superior method of making multiple valve closuremembers or flappers 18 by providing a finished machine flapper 18 whenthe cylindrical sectors are cut out of the tubular member 90.

The present invention, therefore, is well adapted to carry out theobjects and attain the ends and advantages mentioned as well as othersinherent therein. While a presently preferred embodiment of theinvention has been given for the purpose of disclosure, numerous changesin the detail of construction and arrangement of parts, and steps of themethod will be readily apparent to those skilled in the art and whichare encompassed within the spirit of the invention and the scope of theappended claims.

What is claimed is:
 1. A method of making an arcuate valve closuremember for a subsurface well safety valve comprising,honing the insideof a circular tubular member for providing a finished concave sealingsurface, and cutting a circular sector with a hinge out of the tubularmember.
 2. The method of claim 1, including,cutting a second circularsector with a hinge out of the tubular member wherein the second sectoris diametrically opposite to the first sector.
 3. The method of claim 2wherein the first and second sectors and hinges are simultaneously cutout of the tubular member.
 4. The method of claim 1 wherein the cuttingis performed by an electric discharge machine.
 5. The method of claim 1wherein holes are drilled into the tubular member before cutting out thecircular sector and hinge for forming a hinge hole in the cut out valveclosure member.
 6. The method of claim 1 wherein the hinge includes alongitudinal axis and the hinge axis is cut out of a portion of thetubular member which is parallel to the longitudinal axis of the tubularmember.
 7. The method of claim 1 including,applying a hard seat coatingto the inside of the tubular member prior to honing.
 8. A method ofmaking an arcuate valve closure member for a subsurface safety valvecomprising,honing the inside of a circular tubular member for providinga finished concave seat surface, simultaneously cutting first and secondcircular sectors, each of which includes a hinge, out of the tubularmember wherein the second sector is diametrically opposite to the firstsector, and prior to cutting out the sectors, drilling a hole throughthe tubular member in a circular plane perpendicular to the axis of thetubular member for forming hinge holes in the cut out valve closuremembers.
 9. The method of claim 8 wherein the cutting is performed by anelectric discharge machine.
 10. The method of claim 8 wherein the hingeincludes a longitudinal axis and the hinge axis is cut out of a portionof the tubular member which is parallel to the longitudinal axis of thetubular member.
 11. The method of claim 8 including,applying a ceramichard seat to the inside of the tubular member prior to honing.